4.9-stable review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
commit 3510c7aa069aa83a2de6dab2b41401a198317bdc upstream.
The recent fix for adding rwsem nesting annotation was using the given "hop" argument as the lock subclass key. Although the idea itself works, it may trigger a kernel warning like: BUG: looking up invalid subclass: 8 .... since the lockdep has a smaller number of subclasses (8) than we currently allow for the hops there (10).
The current definition is merely a sanity check for avoiding the too deep delivery paths, and the 8 hops are already enough. So, as a quick fix, just follow the max hops as same as the max lockdep subclasses.
Fixes: 1f20f9ff57ca ("ALSA: seq: Fix nested rwsem annotation for lockdep splat") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/sound/seq_kernel.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/include/sound/seq_kernel.h +++ b/include/sound/seq_kernel.h @@ -49,7 +49,8 @@ typedef union snd_seq_timestamp snd_seq_ #define SNDRV_SEQ_DEFAULT_CLIENT_EVENTS 200
/* max delivery path length */ -#define SNDRV_SEQ_MAX_HOPS 10 +/* NOTE: this shouldn't be greater than MAX_LOCKDEP_SUBCLASSES */ +#define SNDRV_SEQ_MAX_HOPS 8
/* max size of event size */ #define SNDRV_SEQ_MAX_EVENT_LEN 0x3fffffff